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Equipment Discussions >> ATM, Optics and DIY Forum

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Mr Magoo
Carpal Tunnel
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Reged: 11/05/05

Loc: Indiana
Re: Mirror Cell new [Re: Pinbout]
      #5618930 - 01/12/13 12:00 PM

Very cool. I'm playing with PLOP this morning. I also just checked my mirror and it is actually 1" thick, not 1.1". Not sure how much that changes things. Do you use the automatic cell design?

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Pinbout
Postmaster
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Reged: 02/22/10

Loc: nj
Re: Mirror Cell new [Re: Mr Magoo]
      #5619016 - 01/12/13 12:53 PM

Quote:

Do you use the automatic cell design?




yeah.

what's really cool is make the design and get the colored plot and go back and make changes and watch the colored plot automatically change/morph.


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Mr Magoo
Carpal Tunnel
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Reged: 11/05/05

Loc: Indiana
Re: Mirror Cell new [Re: Mr Magoo]
      #5619025 - 01/12/13 12:56 PM Attachment (14 downloads)

Okay, I ran this through with better numbers that I should have checked first, my apologies for that. My memory is not as good as I thought. Diameter= 332.74mm, focal length= 1480.693mm, thickness= 25.4mm, obstruction= 78.74. I used the Automatic Cell Design feature and came up with this for a 6 point cell.

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Mr Magoo
Carpal Tunnel
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Reged: 11/05/05

Loc: Indiana
Re: Mirror Cell new [Re: Pinbout]
      #5619269 - 01/12/13 03:25 PM

For some reason I can't save that as a .dwg file. I'm not even getting the option to. I have a design question for the masses. What do you use as the support point? Furniture pads, nylon screws, ...?

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Pinbout
Postmaster
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Reged: 02/22/10

Loc: nj
Re: Mirror Cell new [Re: Mr Magoo]
      #5619298 - 01/12/13 03:35 PM

Save the txt file the rename the extension to dwg

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Mr Magoo
Carpal Tunnel
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Reged: 11/05/05

Loc: Indiana
Re: Mirror Cell new [Re: Mr Magoo]
      #5619341 - 01/12/13 04:02 PM Attachment (14 downloads)

Here is the info I used from what I ran.

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Mr Magoo
Carpal Tunnel
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Reged: 11/05/05

Loc: Indiana
Re: Mirror Cell new [Re: Mr Magoo]
      #5619354 - 01/12/13 04:08 PM Attachment (11 downloads)

This is what I drew from that for the layout. Does this look correct?

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Pinbout
Postmaster
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Reged: 02/22/10

Loc: nj
Re: Mirror Cell new [Re: Mr Magoo]
      #5619530 - 01/12/13 05:48 PM

Great, it's cool to do it yourself. Stupid iPod won't let do a gremlin.

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derangedhermit
Pooh-Bah


Reged: 10/07/09

Loc: USA
Re: Mirror Cell new [Re: Mr Magoo]
      #5619791 - 01/12/13 08:44 PM

Quote:

Seems like it because the right one has 6 clearly defined spots. I'm assuming that the big red donut hole in the center of the right one is not good.



The center of the mirror is in the shadow of the diagonal, so it doesn't matter.


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Mr Magoo
Carpal Tunnel
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Reged: 11/05/05

Loc: Indiana
Re: Mirror Cell new [Re: Pinbout]
      #5620057 - 01/13/13 12:16 AM

My AutoCad skills are a little rusty. Took me a bit. I'm going to try and do the 9 and 18 also. Can't do the 3D although I do have the full version. Never got that far in school.

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Pinbout
Postmaster
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Reged: 02/22/10

Loc: nj
Re: Mirror Cell new [Re: Mr Magoo]
      #5620319 - 01/13/13 09:03 AM

I do my 3d work in 3dmax. I use to be able to work 3d in autocad but that was a long time ago.

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Ajohn
sage
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Reged: 12/03/07

Re: Mirror Cell [Re: Pinbout]
      #5621060 - 01/13/13 03:28 PM

Never used one of these types of supports as when I made mirrors the blank thinknesses were ok. A thought has struck me though, Be interested in comments. As I am probably going to be making another in the near future.

Taking ferric stainless as that has a low coifficient of expansion it's 10um/m/C. Aluminium is a bit more than twice this. If the support bars are 50mm long they change at 1/20 of that or 500nm / C so if there is a temperature difference of 1/250 C there is 2nm difference in the support height and it's hard to imagine them all being at the same temperature to that sort of accuracy and plop goes the mirror. I have also heard of people testing mirrors mounted like this and running into problems even when they are lying flat which sort of suggests the problems are more than 2nm. I also feel it would take a pretty thick backing plate to limit deflection to that sort of extent so also just how thick does that have to be?

John
-


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Don H
sage


Reged: 12/28/06

Loc: Midwest US
Re: Mirror Cell new [Re: mark cowan]
      #5621724 - 01/13/13 09:29 PM Attachment (9 downloads)

I made a 13" f/5.3 a few years ago and used PLOP for the cell design. The pads were nylon floor glides. It seemed to work nicely.

Regards,
Don


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Mr Magoo
Carpal Tunnel
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Reged: 11/05/05

Loc: Indiana
Re: Mirror Cell new [Re: Don H]
      #5621840 - 01/13/13 10:30 PM

That looks great Don! Thank you for the picture. I would love to see if others want to post them. I'm especially interested in what you use for the pivot points on the bars or triangles.

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Arjan
super member


Reged: 01/21/09

Loc: Netherlands
Re: Mirror Cell new [Re: Mr Magoo]
      #5622748 - 01/14/13 02:04 PM

For a single bar pivot point: 1cm dab of silicone.
Mirror can slide loosely though, on ball bearings.
You build the cell on the back of the mirror, use about 2mm thickness of silicone.


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